In recent years, mobile communication terminals such as cellular phones or mobile terminals have been rapidly developed. Radio waves reaching mobile communication terminals from a base station are changed to multiple waves by reflection, scattering, diffraction or the like due to the geographical features of a propagation path thereof, structures or the like, and the amplitude and phase of radio waves vary randomly with location. When radio waves from a base station are received while moving within the propagation path, fading due to the multi-path propagation of radio waves occurs. As a result, code errors increase in a digital communication environment, and transmission qualities considerably deteriorate. For this reason, when the communication performance of the mobile communication terminal is evaluated, devices referred to as a fading simulator that simulates a radio wave propagation environment are used along with base station pseudo devices obtained by simulating a base station.
When tests under a plurality of radio wave propagation environments are continuously performed by changing a plurality of parameters, it is preferable that operations of a fading simulator can be changed in a state where connection between the base station pseudo device and the mobile communication terminal is maintained. For this reason, for example, a fading simulator disclosed in Japanese Unexamined Patent Application Publication No. 2009-188932 is proposed.
The fading simulator disclosed in Japanese Unexamined Patent Application Publication No. 2009-188932 includes a signal processing unit that performs a process of simulating a transmission path with respect to an input signal, and sequentially outputs initial effective process results obtained with respect to the input signal, a signal bypass unit that accumulates the input signal, and starts to read out the accumulated input signal in accordance with a timing at which the initial effective process results are output from the signal processing unit, a signal selection unit that selectively outputs either an output of the signal processing unit or an output of the signal bypass unit, and a control unit that outputs the output of the signal processing unit from the signal selection unit in a period except a period in which a change process of a parameter or a function for the signal processing unit is performed, and outputs the signal, which is read out from the signal bypass unit, from the signal selection unit in a period in which the change process is performed.
In Japanese Unexamined Patent Application Publication No. 2009-188932 having such a configuration, since the signal processing unit notifies the signal bypass unit of an output timing of initial effective process result data obtained with respect to the input signal, and starts to read out the input signal accumulated by the signal bypass unit in accordance with a timing of the notification, a delay of the signal bypass unit can be automatically conformed to the same delay as that of the signal processing unit, and thus signal interruption does not occur at the time of a change in the parameter.